Water can condense on the heat exchangers (e.g., evaporator fins and cooling coils) or drain pans of heating, ventilating and air conditioning (HVAC) units, thereby providing a favorable environment for microorganisms (e.g., mold, pollen, bacteria etc. . . . ). The presence of such materials can detrimentally affect the quality of air passed through the heat exchanger. In some cases ultraviolet (UV) light is used to degrade or kill the microorganisms. UV light exposure however, can degrade UV-sensitive components in a HVAC unit, thereby shortening the operable lifetime of these components. UV light exposure can also damage human tissue (e.g., the eyes) thereby presenting a potential hazard to individuals servicing HVAC units.